Thomas Fuller, an African sold into slavery in 1724 at the age of 14,was sometimes known as the "Virgina Calculator " from his extra ordinary ability to solve complex maths problems in his head.He was asked how many questions there was in a year and a half,he answered in about 2 minutes, 47,304,000.
Again he was asked how many seconds a man who is 70 years,17 days and 12 hours old has lived, he answered in a minute and a half 2,210,500,800.One of the men was working out the problem on paper,and informed Fuller that he was wrong,because the answer was much smaller.Fuller hastily replied,"Top,massa, your forgot the leap year".When the leap year was added, the sum matched.Source: Black History-Jac King.